The overall goal of this research is to determine the molecular mechanisms that control the expression of the human MnSOD gene during tumor promotion. It is well documented that MnSOD level is altered in transformed cells. Our previous studies demonstrate that overexpression of the MnSOD gene suppresses tumorigenesis in a multistage skin cancer model. However, when and how MnSOD expression is modulated during carcinogenesis is unknown. We have generated several lines of transgenic mice expressing a luciferase reporter gene under the control of MnSOD promoter/enhancer elements. This unique animal model provides an outstanding opportunity for investigating changes in MnSOD expression during the carcinogenesis process in animals by a non-invasive method. We hypothesize that repetitive exposure to tumor promoter leads to inactivation of MnSOD expression. Specific Aim 1 will determine at what point the expression of MnSOD is reduced during the process of cancer development using transgenic mice harboring a MnSOD promoter-driven luciferase reporter and bioluminescence-imaging strategies to noninvasively and quantitatively image MnSOD expression in living mice. Specific Aim 2 will investigate how changes in MnSOD expression occur in vivo using chromatin immunoprecipitation (ChIP) assays, DNA sequencing, and proteomic analyses. Specific Aim 3 will identify transcription factors and co-activators/repressors necessary for transcriptional modulation of the MnSOD gene using DNA binding, siRNA, and protein/protein interaction methods. The results of the proposed studies will provide information on when and how the expression of MnSOD is altered during tumorigenesis. Because of the essential role of MnSOD for the survival of aerobic life and its well documented role in the prevention of oxidative stress-mediated tissue injury and cancer formation, understanding how the expression of MnSOD can be regulated during cancer development is likely to have broad implications for the prevention of cancer.